Smart sat-nav cuts through jams

A system that brings together satellite navigation and mobile phones can detect when cars slow down and use that information to warn other drivers about traffic jams as soon as they begin to form. One such system is already in use, turning mobile phones into beacons, like the transponders that let air traffic controllers keep tabs on incoming aircraft. It and its competitors could, in theory, record the speed and location of almost every vehicle on the road.

While basic sat-nav traffic updates have been available for some years now, the new technology differs greatly from what has come before. It's very close to reality, too. TomTom has already introduced its HD Traffic service, which makes use of the new system, and NAVTEQ has acquired similar technology by buying T-Systems Traffic. It expects to bring this to consumer devices in the near future.

The existing system involves a combination of fixed cameras, fleet vehicles with sensors and FM radio transmission. Thousands of number-plate readers owned by Trafficmaster placed at key points on major routes in the UK track the movements of passing vehicles, using the information to calculate the traffic speed. When it falls significantly below what it should be for the road in question, an alert is generated.

This is where the FM radio comes in. The RDS signal that tells your radio receiver the name of the channel you have tuned into can also be used to transmit other text information. So RDS-based updates from Trafficmaster piggyback on radio signals, which can be picked up by some sat-nav devices and overlaid onto maps. This system has its drawbacks. The Trafficmaster network only covers motorways and 95 per cent of trunk roads. It won’t pick up problems on local streets at all. Similarly, the fleet vehicle service only includes about 50,000 cars, which is a miniscule sample of the more than 30 million vehicles on UK roads.

By contrast, the new systems from TomTom and NAVTEQ could eventually extend to almost all of them. Instead of using fixed cameras or a small sample of vehicles which do a lot of miles, these systems hook into mobile phones to assess traffic speeds. Your mobile phone carrier always knows approximately where your phone is, in order that it can route calls to the appropriate radio tower. The strength of the signal between the handset and nearby towers can therefore be used to track its precise location. This isn’t quite as accurate as GPS, but in urban areas with a high density of towers it can get pretty close, as original iPhone users and followers of the TV series 24 will attest.

This data can be correlated with map data and used to derive the traffic speed on roads, which in turn generates congestion alerts. With more than 70 million phone handsets in use the UK, the accuracy of traffic flow data obtained using this method is potentially very great indeed. TomTom already tracks up to 16.7 million mobile phones for its HD Traffic system, which covers all motorways and A-roads in the UK. Its updates are delivered over a mobile data connection to the sat-nav device every three minutes, which is considerably more frequent than the 15-minute cycle of RDS-TMC. You can see the system of congestion alerts in action at this website.

The privacy implications are potentially unsettling, even though the companies assure us that the information is entirely anonymous. The Trafficmaster camera system, for example, has already been attacked by lobby groups such as CameraWatch, who say it could provide a way of tracking the average speeds of individual vehicles for prosecution purposes. Mobile phone-based traffic monitoring may actually reduce that risk, since there is no easy and legally robust way of linking a phone with a car.

Most people have already agreed to have their locations tracked, since mobile phone terms and conditions include that provision so that operators can monitor network traffic and keep data flowing smoothly. The information needed to keep road traffic moving can be entirely anonymous, but the fact that such details are being collected and analysed will appear to some as the thin end of the wedge.

Even so, the advantages are clear. Sat-nav devices with this kind of real-time traffic information are already proving effective, helping users avoid jams as they develop and therefore helping to prevent further build-up of traffic. In spite of the privacy concerns, mobile phone-linked sat-nav may be just the technological solution we need to keep UK roads driveable.